Hi all, I am hopeful some one might be able to point me in the right direction. When i am motoring on the boat, and go over about 1200 rpm there is a knocking sound that is in time with the engine revs, in the past i have had the prop balanced, i have replaced the cutless bearing, and removed and had the propeller shaft balanced, After all this the knocking sound is still there, although it was a little less at first, but is now back to how it was in the past. I noticed that part of one of the rear engine mounts had collapsed or at least appears to have, Would this possibly be the cause of the knocking ??? 
Select to expand quoteBen405 said..
Hi all, I am hopeful some one might be able to point me in the right direction. When i am motoring on the boat, and go over about 1200 rpm there is a knocking sound that is in time with the engine revs, in the past i have had the prop balanced, i have replaced the cutless bearing, and removed and had the propeller shaft balanced, After all this the knocking sound is still there, although it was a little less at first, but is now back to how it was in the past. I noticed that part of one of the rear engine mounts had collapsed or at least appears to have, Would this possibly be the cause of the knocking ???
As the engine mounts had collapsed (or at least appears to have) this would have to be rectified (or at least seen to) in any case, so why not remedy this problem first and see if that cures the knocking issue.
I reckon you might be on the mark there Ben. That one looks to be totally knackered. That one being so bad would mean the others are not far behind.
If all your mounts are as easy to get at as that one, you have a strong argument for converting to solid mounts which your engine will love.
Whether you convert or not is optional but you do need to replace I feel. That of course means doing an accurate engine to prop shaft alignment.
You gotta get rid of the knockery before your engine has to go to the knackery.
Yep, I think they be stuffed.
This must affect the alignment of the prop shaft to the engine coupling greatly-Even a flexible coupling would not cope with that amount of error and a rigid one would positively shake the rest of your teeth out!
